Too slow? we don’t think so. Outcomes relative to embryo development in a busy oocyte cryopreservation (OC) program Sarah Druckenmiller, Frederick Licciardi, Patty Ann Labella, Melicia Clarke-Williams, Nola Seta, David McCulloh, Nicole Noyes Background OC is now a mainstream ART, frequently used to bank donor oocytes or defer fertility. To date, more than 3,000 babies have been born as a result of OC [1-3]. autologous vs. donor thaws only reached Stage 2 (p<.01). When comparing pregnancy rates between autologous and donor cycles relative to the day (D) blastocysts were transferred (i.e. D-5 vs. D-6/7 post-ICSI), no statistical difference was noted when similarly-staged blastocysts were transferred whether they reached the stage on D-5 (24/53 {45%} vs. 16/28 {57%};p=0.4) or D-6/7 (1/3 {33%} vs. 1/1 {100%};p=1); however, within the autologous and donor groups, implantation rates were significantly higher with transfer of blastocysts greater than Stage 1; p<.04 (See Bar Graph). Finally, blastocyst formation rates for age-matched FRESH autologous (959/1539; 59%) and donor (2578/3658; 71%) cycles were significantly higher when compared to those of frozen autologous and donor cycles; p<.01. Embryo Development of Thawed Autologous Oocytes vs. Thawed Donor Oocytes Highest Stage of Embryo Development Achieved Autologous OC (n=1098) Donor OC (n=411) P Value 2PN-Zygotes with No Division (1-cell) 7% (81) 9% (39) 0.2 2PN-Zygotes with Cleavage Arrest 39% (433) 34% (139) 0.04 Morula 14% (156) 15% (60) 0.9 Blastocyst - Stage 1 7% (75) 5% (22) Blastocyst - Stage 2 17% (181) 8% (33) <0.01 Blastocyst- Stage 3 8% (84) 12% (49) 0.02 Blastocyst- Stage 4+ 8% (88) 17% (68) Objective We analyzed the specifics of post-fertilization embryo development in order to glean outcome differences between autologous (older) and donor (younger) frozen-thawed oocytes. We also compared OC blastocyst formation rates to those of FRESH-oocyte cycles. Materials and Methods For OC, 154 autologous (139 patients) and 53 donor (no commercial-bank oocytes) thaw procedures completed from 2004-2015 were reviewed. Cycle data was mined for: oocyte maturity, survival, 2-pronuclear (2PN) fertilization, embryo development, implantation and pregnancy rates. When assessing embryo development, the highest stage and grade achieved before transfer was used. Blastocysts were graded using Gardner’s criteria. When evaluating implantation and pregnancy rates relative to blastocyst stage at transfer, only single-embryo or multi-embryo transfers with same-stage embryos were considered. Blastocyst formation rates in 286 age-matched FRESH autologous and 186 FRESH donor cycles from 2011-2014 were computed and compared to retrospective OC thaw outcomes. Fisher’s exact test was used for statistics. 20% 28% 42% 40% Implantation and Pregnancy Rates Relative to Embryo Stage at Transfer for OC thaws with Autologous and Donor Oocytes 19% 17% 13% Blastocysts: Highest Stage Achieved Conclusions Blastocyst formation rates in autologous vs. donor OC cycles were not different, although both were lower than in autologous and donor FRESH cycles. In the OC cycles with no blastocysts formation, most embryos arrested during the cleavage stage, but ~8% failed to divide entirely. Twenty-one percent reached morula or Stage-1 blastocyst, both considered early “usable” embryos that result in reasonable, albeit lower, implantation and pregnancy rates. When comparing blastocyst maturity in autologous vs. donor cycles, donor oocytes achieved greater blastocyst expansion as well as higher implantation and pregnancy rates, most likely reflecting superior gamete status secondary to younger oocyte age. Results For OC, 1,098 autologous (7/cycle; mean age 38±3y; range 25-44y) and 411 donor (8/cycle; mean age 27±5y; range 22-33y) oocytes were thawed, survived and achieved 2PN fertilization. OC blastocyst formation rates were not different when comparing autologous (n=428 ; 40%) vs. donor (n=173; 42%) rates; however, within the blastocyst stage groups, more blastocysts expanded to Stage 3 and Stage 4 in donor than autologous cycles; p<.02 (See Table and Pie Graphs). Conversely, a greater percentage of blastocysts in the Percent References Noyes N, Porcu E, Borini A. With ore than 900 babies born, birth outcomes following oocyte cryopreservation do not appear different from those occurring after conventional IVF. Reprod Biomed Online. 2009;18:769-76. Cobo A, Garrido N, Pellicer A, Remohi J. Six year experience in ovum donation using vitrified oocytes, report of cumulative outcomes, impact of storage time and development of a predictive model for oocyte survival. Fertil Steril doi 10.2016/jfertmstert 2015.08.020. SART.org. 2013 statistics.